Rendering cellulosic material nonadherent to adhesives



Patented Mar. 11, 1952 RENDERING CELLULOSIC MATERIAL NON- ADHERENT TOADHESIVES Firth L. Dennett, Midland, Mich., assignor to Dow CorningCorporation, Midland, Mich., a corporation of Michigan No Drawing.Application May 4, 1950, Serial No. 160,098

6 Claims. (Cl. 260-13) The present invention relates to methods ofrendering cellulosic fibrous sheet material nonadherent to variousorganic solids. It is particularly concerned with methods of renderingpaper or paperboard non-adherent to normally adherent material such asasphalt, rubber, and high molecular weight organic polymers.

Cellulosic materials impermeable to asphalt have heretofore beenprepared by depositing a double coating upon the cellulosic material.The first coating Was of clay; the second, of methylcellulose andstarch. A method such as this, however, is expensive and changes thephysical nature of the material to which it is applied.

It is an object of the present invention to provide an improved methodfor rendering cellulosic fibrous sheet material non-adherent towardmaterials which normally adhere thereto. Further objects are to providenon-adherent cellulosic sheet material of improved water-repellency andgrease-proof characteristics.

It is known that a methylhydrogenpolysil oxane fluid may be cured on asurface to render that surface water-repellent.

It has now been found that the cured methylhydrogenpolysiloxane alsorenders a surface highly non-adherent toward materials which normallyadhere thereto, and that this property can be enhanced by incorporatinga water soluble cellulose ether into the polysiloxane prior to our--ing. When the cellulose ether is present, a given degree ofnon-adherency can be attained with only a fraction of the amount ofsiloxane which would otherwise be needed. Hence, incorporation of thecellulose ether into the polysiloxane results in a process which is muchmore economical and more practical on a commercial scale.

In accordance with a preferred form of this invention, a cellulosicsheet material is wetted with an aqueous emulsion of amethylhydrogenpolysiloxane fluid in an aqueous solution of awater-soluble cellulose ether, and the material dried. The materialbecomes water-repellent, greaseproof, and extremely non-adherent towardnormally adhesive materials. These desirable properties are imparted tothe cellulosic sheet material without any apparent change in texture orcolor, and without altering such physical properties as tensilestrength, tear resistance, or moisture vapor transmission.

The cellulosic materials of concern herein include all types of papers,such as kraft paper, linen rag paper, rice paper, sulfite cellulosepaper and the like; and sheeting or boxing materials such as paperboard,cardboard, pulpboard, and pasteboard.

weight of the cellulose ether.

2 The methylhydrogenpolysiloxane fluids employed in the process of thisinvention are fluids of the empirical formula in which a has a value offrom 1.0 to 1.5, b has a value of from 0.75 to 1.25, and the sum of aand b has a value of from 2.0 to 2.25 inclusive. They may contain tracesof hydroxy radicals due to incomplete condensation, and can be eithercyclic or linear polymers. At least 50 per cent of the siloxane unitspresent in the polymer are of the formula CHsHSiO. The linear polymersmay be end-blocked with units such as trimethylsiloxy ordimethylhydrogensiloxy units. Such fluids are well known to the art.

Any of the water soluble cellulose ethers may be used in the process ofthis invention. Methylcellulose, hydroxyethylcellulose, and the sodiumsalt of carboxymethylcellulose (the glycolic acid ether of cellulose)are preferred. Ethylcellulose may also be used when it is water soluble,i. e. when it has a degree of substitution (average number of ethylgroups per anhydro-glucose unit) of from 0.8 to 1.3. Whenmethylcellulose is used, a viscosity grade of from 15 cps. (centipoises)to 4,000 cps. is preferable. This indication of viscosity grade is theviscosity of a 2' per cent aqueous solution at 20 C.

A preferred mode of operation in the process of this invention is toprepare a stock of an aqueous emulsion of the methylhydrogenpolysiloxanefluid. This stock emulsion is then diluted with the aqueous solution ofthe cellulose ether as needed. The final mixture preferably containsfrom 0.1 to 20 per cent by weight of the polysiloxane, and from 0.1 to10 per cent by Dilution of the polysiloxane emulsion with the celluloseether solution requires no special equipment since the two are readilycompatible. If desired, rather than diluting themethylhydrogenpolysiloxane stock emulsion with the cellulose ethersolution, the working emulsion may be prepared directly by emulsifyingthe methylhydrogenpolysiloxane fluid in the cellulose ether solution.

In preparing an aqueous emulsion of the methylhydrogenpolysiloxanefluid, it is preferable to use a colloid mill or other very high speedmixer. Any conventional emulsifying agent may be used with satisfactoryresults. For improved water repellency in the treated product, however,it is preferred to employ quaternary ammonium salts or the higheraliphatic alcoholsul phates. The amount of the emulsifying agent used inthe emulsion will, of course, depend upon the particular agent used.When a higher aliphatic alcohol sulphate is used, it is preferred toemploy about per cent by weight based on the amount ofmethylhydrogenpolysiloxane fluid present. When this emulsion is to beused primarily as a stock emulsion, to be diluted with the solution ofcellulose ether prior to its actual use, any convenient ratio ofmethylhydrogenpolysiloxane to water may be used. For ease of preparationand convenience in storing, a concentration of about 50 per centpolysiloxane is preferable. '1he methylhydrogenpolysiloxane emulsionstend to liberate hydrogen upon standing. It is accordingly desirable toadd an organic acid such as acetic acid to the emulsion in order toinhibit such evolution of silane hydrogen.

Catalysts may be incorporated into the emulsion to speed up the curingrate of the methylhydrogenpolysiloxane fluid. A wide choice of suchcatalysts is available, since any metal salt of a carooxylic acid isapplicable. The lead, iron, and zinc salts of carboxylic acids arepreferred, particularly the acetates, hexoates, octoates, oleates,stearates, napntnenates, laurates, and resinates. The copper, aluminum,magnesium, cadmium, cobalt, nickel and sodium salts are also effective.Catalysts such as sodium bicarbonate and sodium aluminate may alsobeused. The catalyst is preferably employed in such an amount that thereis from 0.5 to 4.0 per cent by Weight of the metal constituent present,based on the weight of the siloxane. .The catalyst should be added justprior to the application of the emulsion.

The final emulsion mixture can be applied to the material to be treatedby any convenient method. when applied to paper, the conventional dip orroller coating equipment may be used, or the emulsion may be applied ona size press connected with the paper machine.

The amount of siloxane polymer which is picked up by the material to betreated depends upon the absorbency of the material, the applicationmethod, and the concentration of siloxane in the emulsion. The pickupdesirable for optimum non-adherency and water-repellency properties willvary with the type of cellulosic mate.- rial being treated. Ordinarily,the preferred pickup of siloxane is from 0.25 to 4.0 per cent, based onthe dry weight of the cellulosic material, and the preferred pickup ofcellulose ether is from 0.1 to 3.0 per cent. Of course a greater pickupmay be used, but it is not ordinarily neces- Following the wetting ofthe cellulosic mate rial, it is dried. This drying step also results inthe release of hydrogen from the methylhydrogenpolysiloxane fluid andits attendant cure. This drying or curing can be accomplished at roomtemperature, but in order to speed up the process and to develop maximumnon-adherency immediately, it is preferable to apply heat. In general, atemperature of from 40 to 200 C. is preferred, with longer timesof'exposure being used at the lower temperatures. A period of from 20 to180 seconds at 150 C. has been found adequate to completely dry and curethe wetter material when a catalyst is present.

ce lulosic materials treated as described above have a wide range ofutility. For instance, asphalt or high molecular weight organic polymerssuch as polyisobutylene may be poured hot into containers fashioned fromthe treated paper or paperboard. After cooling, the solidified asphaltor polymer is easily and cleanly separated from the container walls.

Paper treated in accordance with this invention may be used in contactwith the adhesive surfaces of electricians pressure sensitive tape,adhesive tapes used for surgical purposes, and regenerated cellulosetapes carrying a permanent adhesive upon one surface. Various types offabrics, such as Holland cloth and open weave heavily starehed fabrics,have heretofore been used for this purpose. paper to be substituted forthe indicated fabrics at a very considerable saving in cost.

A still further aspect of the present invention involves the use ofpaper treated as described to prevent sheets of either vulcanized orunvulcanized rubber from adhering together. Thus, rubber compounded inthe customary fashion in a rubber mill is sheeted out and stored assheets. These sheets are sticky and cohere, forming a solid mass. When asheet of paper treated as described is placed between the sheets ofrubber, each sheet may be removed separately and individually withoutdiificulty from sticking. In connectlon with vulcanized rubber,vulcanized sheet rubber could advantageously be cut by stacking sheetsof rubber and die-cutting through all the sheets at once, except thatthis would result in the Various sheets sticking together. Byinterposing treated paper, this sticking is prevented. Many similarinterleaving uses such as this are practical with paper treated inaccordance with this invention.

Paper treated in accordance with this invention is also useful in liningboxes of partially prebaked baked goods such as buns, rolls, and thelixe. Thus, the partially baked goods may be finished on in the originalcontainer and when baking is completed, good release is obtained fromthe liner.

The process of this invention may also be applied to textile fabrics todevelop non-adherent properties thereon.

The following examples describe specific embodiments of the invention,but are not to be construed as limiting the scope thereof. All partsgiven are by weight.

For use in these examples, a master batch of themethylhydrogenpolysiloxane emulsion was made as follows.

A mixture of 1,000 parts of CHsI-ISiClz and 51.5 parts of (CH3)3SiCl wasadded to 750 parts of benzene. This mixture was then cooled to 20C. Tothis mixture 675 parts of isopropyl alcohol were added over a period of10 minutes, and then 783 parts of water were added over a period of onehour; An additional 750 parts of benzene were then added to the reactionmixture. The product was washed six times with water and strip distilledat 3 mm. pressure to C. to remove the benzene and the lower boilingproducts. There were obtained 500 parts of a trimethylsiloxaneend-blocked methylhydrogenpolysiloxane. The 500 parts of methylhydrogenpolysiloxane fluid were slowly addedLwith extremely rapid agitation, toa solution of 50 parts of a higher aliphatic alcohol sulphate (DupanolG) in parts of water. The resulting emulsion was diluted with 300 partsof water, to give a 50 per cent concentration of the polysiloxane. About3 parts of glacial acetic acid were then added, to reduce the pH of theemulsion to about This invention allows treated 6. This emulsion isdesignated hereafter as emulsion A.

A master batch of zinc Z-ethyl hexoate catalyst emulsion was prepared asfollows. Fifty parts of an 8 per cent solution (based on zinc metal) ofzinc 2-ethyl hexoate in naptha were added with extremely rapid agitationto a solution of parts of Dupanol G in 15 parts of water. The resultingemulsion was diluted with 30 parts of water, giving an emulsion whichcontained 4 per cent by weight of zinc metal. This emulsion isdesignated hereafter as emulsion B.

Example 1 A 1.5 per cent aqueous solution of a 4,000 cps. grade ofmethylcellulose was prepared. 185 grams of this solution were added to amixture of 12 grams of emulsion A and 3 grams of emulsion B, giving anemulsion which contained 3 per cent by Weight of the siloxane and 1.4per cent of the methylcellulose. A sheet of 0.023" kraft paperboard wasdipped in this emulsion and passed between squeeze rolls to remove theexcess. The gain in weight represented 0.38 per cent pickup of siloxane.The board was dried for one minute at 150 C. When molten asphalt at 350F. was poured into a container fashioned from this treated board andallowed to cool, excellent release was obtained with no adhesion ofcellulose fibers to the asphalt.

For purposes of comparison, three grams of the zinc catalyst emulsion Band 185 grams of water were added to 12 grams of the 50 per centmethylhydrogensiloxane emulsion A, giving an emulsion which contained 3per cent by weight of the siloxane. A sheet of 0.023" kraft paperboard,weighing 7.35 grams, was dipped in this emulsion and passed betweensqueeze rolls to remove the excess. After squeezing, the weight wasfound to be 10.78 grams, representing a 1.4 per cent pickup of thesiloxane. The board was then dried for one minute at 150 C. Asphalt at350 F. was poured into a container fashioned from this treated board.Upon cooling, the asphalt adhered to the board in many areas. Whenrelease was forced, the surfaces of the solidified asphalt which hadbeen in contact with the container were contaminated with celluloseExample 2 A mixture was made of 40 grams emulsion A, grams emulsion B,67 grams of the 1.5 per cent aqueous solution of 4,000 cps. grademethylcellulose, and 83 grams of water. The resulting emulsion contained10 per cent by weight of the siloxane and 0.5 per cent of themethylcellulose. A 7.39 gram sample of the 0.023" kraft paperboard wasdipped in this emulsion and then squeezed, giving a weight of 8.56grams. This represents 1.6 per cent pickup of the siloxane. The boardwas cured for one minute at 150 C., and excellent release from asphaltwas obtained.

Example 3 A 6 per cent solution of a 50 cps. grade methylcellulose wasprepared. 75 grams of this solution were added to a mixture of 20 gramsemulsion A and 5 grams emulsion B. The resulting emulsion contained 10per cent by weight of the siloxane and 4.5 per cent of the methylcellulose. After dipping and squeezing, an 8.13 gram sample of the .023kraft paperboard weighed 9.51 grams, representing a 1.7 per cent pickupof the siloxane. Molten asphalt was poured into a container fashionedfrom this treated board and allowed to cool. Excellent release of theasphalt from the board was obtained.

Example 4 A 4 per cent solution of 50 cps. grade methylcellulose wasprepared. 75 grams of this solution were added to 16 grams of emulsionA, 4 grams of emulsion B, and 5 grams of water. The resulting emulsioncontained 8 per cent of the siloxane and 3 per cent of themethylcellulose. A 7.59 gram sample of the .023" ,kraft paperboard,after dipping in this emulsion and squeezing, weighed 8.82 grams,representing 1.3 per cent pickup of the siloxane. After curing the boardone minute at 150 0., excellent release from asphalt was obtained.

Example 5 A 7 per cent aqueous solution of 15 cps. grade methylcellulosewas prepared. 75 grams of this solution were added to 20 grams ofemulsion A and 5 grams of emulsion B. This gave an emulsion containing10 per cent of the siloxane and 5.3 per cent of the methyl cellulose.When an 8.4 gram sample of the kraft paperboardwas dipped in thisemulsion and squeezed, a weight of 9.97 grams was obtained, indicating a1.9 per cent pickup of the siloxane. The board was then cured for twominutes at 150 C. Good release from asphalt was obtained.

Example 6 A 1.5 per cent aqueous solution of 4,000 cps. grademethylcellulose was prepared. grams of this aqueous solution were addedto a mixture of 4 grams of emulsion A and 1 gram of emulsion B. Theresulting emulsion contained 2 per cent of the siloxane and 1.4 per centof the methylcellulose. A 2.71 gram sample of kraft paper was dipped inthis emulsion and squeezed to remove the excess. The wet weight of thepaper was 7.04 grams, indicating a 3.2 per cent pickup of the'siloxaneand 2.2 per cent pickup of the methylcellulose. The paper was cured forone minute at C. This paper was contacted with a sheet of low tensilecrude rubber for a period of 5 days at room temperature under a pressureof 5 lbs. per square inch. No adhesion was obtained between the paperand the rubber.

Example 7' To a mixture of 1.8 grams of emulsion A and 0.5 grams ofemulsion B was added 97.7 grams of the 1.5 per cent methylcellulosesolution from Example 6. A 2.49 gram sample of kraft paper was dipped inthis solution and squeezed, giving a weight of 6.05 grams. Thisindicated a 1.3 per cent pickup of the siloxane and a 2.1 per centpickup of the methylcellulose. The paper was cured for one minute at 150C. and contacted with the crude rubber as in Example 6. Excellentrelease between the paper and the rubber was obtained.

Example 8 A one per cent aqueous solution of carboxymethylcellulose(sodium salt) was prepared. 97.5 grams of this solution were added to amixture of 2 grams of emulsion A and 0.5 gram of emulsion B. A sheet ofkraft paper was dipped in this emulsion and squeezed. A 1.2 per centpickup of the siloxane and a 1.10 per cent pickup of thecarboxymethylcellulose were obtained. A portion of the treated paper wasair-dried for one hour. Another portion was cured for one minute at 150C. Scotch Tape" would not adhere to either portion.

Example 9 Ewample 10 Emulsions of iron octoate and lead naphthenate wereprepared, using the procedure employed for the preparation of emulsionB. Each emulsion was adjusted to a 4 per cent by weight content ofmetal. When Example 6 was repeated, replacing the zinc catalyst witheither the iron or lead salts from above, the results comparable withthose obtained in Example 6.

That which is claimed is:

1. The method of rendering cellulosic fibrous 7 sheet materialnon-adherent toward materials which normally adhere thereto whichcomprises Wetting the material with an aqueous emulsion ofa'methylhydrogenpolysiloxane fluid of the empirical formula in which ahas a value of from 1 to 1.5, b has a value of from'0.75 to 1.25, andthe sum of a and b has a value of from 2.0 to 2.25 inclusive, in anaqueous solution of a water soluble cellulose ether; said emulsioncontaining from 0.1 to per cent by weight of themethylhydrogenpolysiloxane fluid and from 0.1 to 10 per cent by weightof the cellulose ether; and drying the wetted material.

2. The method of rendering cellulosic fibrous sheet materialnon-adherent toward materials which normally adhere thereto whichcomprises wetting the material with an aqueous emulsion of amethylhydrogenpolysiloxane fluid of the empirical formula 'inwhich a hasa value of from 1 to 1.5, bhas a value of from 0.75 to 1.25, and the sumof a and b has a value of from 2.0 to 2.25 inclusive, in an aqueous.solution of a water soluble cellulose.

ether; said emulsion containing from 0.1 to 20 per cent by weight of themethylhydrogenpolysiloxane fluid, from 0.1 to 10 per cent by weight ofthe cellulose ether, and a metallic salt or" a 'carboxylic acid; anddrying the wetted material.

3. The method of claim 2 wherein the cellulose ether is selected fromthe group consisting of methylcellulose and the sodium salt ofcarboxymethylcellulose, and the metallic salt is selected from the groupconsisting of the carboxylates of lead, zinc, and iron.

4. A composition for rendering cellulosic fibrous sheet materialnon-adherent toward materials which normally adhere thereto, comprisedof an aqueous emulsion of a methylhydrogenpolysiloxane fluid of theempirical formula in which a has a valueof from 1 to 1.5, b has a valueof from 0.75 to 1.25, and the sum of a and b has a value of from 2.0 to2.25 inclusive, in an aqueous solution of a water soluble celluloseether; said emulsion containing from 0.1 to 20 per cent by weight of themethylhydrogenpolysiloxane fluid and from 0.1 to 10 per cent by weightof the cellulose ether.

5. A composition for rendering cellulosic fibrous sheet materialnon-adherent toward materials which normally adhere thereto, comprisedof an aqueous emulsion of a methylhydrogenpolysiloxane fluid of thegeneral formula in which a has a value of from 1 to 1.5, b has a valueof from 0.75 to 1.25, and the sum of a and b has a value of from 2.0 to2.25 inclusive, in an aqueous solution of a water soluble celluloseether; said emulsion containing from 0.1. to 20 per cent by weight ofthe methylhydrogenpolysiloxane fluid, from 0.1 to 10 per cent by Weightof the cellulose ether, and a metallic salt of a carboxylic acid. 7

6. The composition of claim 5 wherein the cellulose ether is selectedfrom the groups consisting of methylcellulose and the sodium salt ofcarboxymethylcellulose, and the metallic salt is selected from the groupconsisting of the carboxylates of lead, zinc, and iron.

- FIRTH L. DENNE'I'I.

No references cited.

1. THE METHOD OF RENDERING CELLULOSIC FIBROUS SHEET MATERIALNON-ADHERENT TOWARD MATERIALS WHICH NORMALLY ADHERE THERETO WHICCOMPRISES WETTING THE MATERIAL WITH AN AQUEOUS EMULSION OF AMETHYLHYDROGENPOLYSILOXANE FLUID OF THE EMPIRICAL FORMULA